Fabric cleaning compositions comprising an oxygen-based bleach source are well known in the art. Oxygen-based bleach sources are often used as they provide excellent cleaning of stains from fabrics.
Hueing agents are also well known in the art. Over time, fabrics tend to yellow or become grey. This is due to soils present in the wash liquor (having been removed from stains on the fabrics), re-depositing onto the fabric surface. Hueing agents are a class of organic compounds which are used to improve the whiteness of fabrics following the wash process. They are characterised by having a peak adsorption wavelength such that they can deliver a blue or violet shade on white fabrics, making them appear brighter. This alleviation of the yellowing or graying of fabrics is often called fabric whitening or shading.
Thus, there is a continuing need in the art for a composition that provides the excellent cleaning benefits associated with the presence of an oxygen-based bleach source and the excellent fabric whiteness benefits associated with the presence of a hueing agent.
Many hueing agents are not stable in liquid products comprising oxygen-based bleach sources. The hueing agent tends to break-down or decompose in the cleaning composition over time. Furthermore, there is a distinctive change in colour of the composition due to the loss in concentration of the hueing agent (hueing agents have a distinctive blue or violet colouration). Lastly, the loss in concentration of the hueing agent over time results in a decrease in performance of the composition.
It was surprisingly found that hueing agents present in oxygen-based bleach source comprising compositions wherein the composition has a specific pH of between 2.5 and 5.5 were stable.
These compositions allowed for the dual benefit of both the oxygen based bleach source and the hueing agent.